Many ink jet print heads use piezoelectric (PZT) elements. The ink jets that use these elements may have a stack of plates, referred to as a jet stack, that form ink manifolds and pressure chambers, with a final plate with an array of nozzles or jets. When the PZT elements receive electrical signals, they deform membranes located adjacent to pressure chambers and cause them to eject ink.
The piezoelectric elements provide a predominantly capacitive load to the drive electronics. The energy stored in the element's capacitance is much larger than the actual energy converted to mechanical/fluid motion. Typically, excess energy dissipates as heat when the elements discharge back to the quiescent voltage level. This energy could be captured and returned to the DC power source of the drive electronics.
Circuits for driving PZT elements with energy recovery exist, but they only contemplate systems with single or a few actuators. These circuits typically require an inductor per actuator. This is impractical for a typical print head with hundreds or thousands of actuators.